The present invention relates generally to infusion cannulae, and more specifically to devices for protecting a needle and the point of the needle, both before and after use of such infusion cannulae.
The existence of serious infectious diseases, such as AIDS and hepatitis, which may infect medical personnel through blood, other body fluids or tissue parts, makes the treatment and the care of patients extremely risky, as each patient is a potential source of infection.
After the discovery of HIV, a large number of people in the medical service, ambulance personnel, nurses, doctors and others, have been infected, e.g. by physical contact with or an inadvertent stick by an infected needle that has been used when treating blood-infected patients.
To protect medical personnel who are directly involved in the care of such highrisk patients, intense work has been done to develop syringes and infusion cannulae as well as protective means in such syringes and infusion cannulae to prevent physical contact with an infected needle and protect against inadvertent needle stick.
One example of such a device is described in U.S. Pat. No. 4,957,488, where a catheter is arranged inside a divided needle and where means is provided for preventing puncture of the catheter by unintentional forward displacement of the needle, once the withdrawal of the needle has been commenced. When the entire needle has been withdrawn, different components are detached, such as a part of an extension hose, which is quite unacceptable in view of the risk of infection.
Another example of a protective device of the above-mentioned type is disclosed in U.S. Pat. No. 4,950,252. Use is here made of an elongate sheath cooperating with needle-protecting means. In an initial position, the needle and the catheter, supported by the needle, extend from one short side of the sheath. In conjunction with the withdrawal of the needle, said means is displaced relative to the sheath, and the used needle is thus retracted into the needle protecting means.
Yet another example of such a device is described in U.S. Pat. No. 4,917,669, where a needle-supporting means is arranged in an elongate sheath for longitudinal displacement therein. In an initial position, the needle is located within the sheath. By axial displacement of said means relative to the sheath, the needle and the catheter, supported by the needle, are extended from one short side of the sheath. When the catheter has been placed in the patient's vein, the procedure is reversed, i.e. the needle is retracted relative to the sheath so as finally to be enclosed thereby.
U.S. Pat. No. 4,850,961 describes a device which in this context must be considered to represent the closest prior art. Also in this device, the needle and the catheter, supported by the needle, are initially located inside an elongate sheath. In this case too, a needle-supporting means is operated to release the needle and the catheter by axial displacement of said means relative to the sheath. At the end of the reversed procedure, i.e. in conjunction with the withdrawal of the used needle, a lug, employed for displacing said means, enters a recess provided in the sheath and not accessible from outside, which means that the lug cannot be used again for extending the needle. This prior-art solution however suffers from a number of drawbacks. One is that the lug, employed for displacing the needle-supporting means, will be located, in the extended position of the needle, at a relatively great distance from the point of the needle. To guide the needle or control the movement of the point of the needle as accurately as possible, the device should however be gripped as far towards the anterior end as possible. Such anterior gripping is however not feasible, since the needle and the catheter supported by the needle would be retracted into the sheath if the grip about the lug is released. Another drawback of this device will be described below.
The known art thus provides different solutions for protecting medical personnel and others from used, possibly contaminated needles. However, all the known solutions suffer from more or less serious drawbacks. The loosening or detaching of parts after use of the needle, which is the case in the device disclosed in U.S. Pat. No. 4,957,488, is of course quite unacceptable. Also in the devices described in U.S. Pat. No. 4,917,669 and 4,850,961 there is considerable risk of unintentional or intentional exposure of the used needle.
In the device of U.S. Pat. No. 4,917,669, the needle is, after use, located in a sheath enclosing it. The short side of the sheath through which the needle and the catheter pass is however open, which is unsatisfactory, even if the point of the needle is located within the sheath and there is no imminent risk, in normal use of the device, of inadvertent contact with the needle point. The needle is locked in this end position by the same mechanism as is used for fixing the needle in the corresponding position prior to use of the device. In a preferred embodiment, this mechanism consists of a recess which is formed in an elongate slot provided in the sheath, and which comprises regions of the slot having a reduced width, the recess and said regions of reduced slot width cooperating with an operating member of the needle-supporting means, which passes through said slot. It will be appreciated that such a mechanism does not offer any adequate protection against renewed extension of the needle, especially since the locking mechanism can be damaged in connection with the use of the device. Moreover, a disadvantageous effect is that blood adhering to the needle after use may drip through the open short side in the sheath or through the slots formed in the sheath.
Attempts have been made to solve the problems discussed with reference to U.S. Pat. No. 4,917,669, by means of the device according to U.S. Pat. No. 4,850,961. As mentioned above, this device has an elongate slot in the sheath which encloses the needle both before and after use of the device. Through this slot passes a lug which is connected to a needle-supporting means and which is displaced relative to the sheath for extending and withdrawing the needle. After the needle has been used, the lug should be retracted so far as to enter a recess in the sheath, whereby it becomes inaccessible to the operator and thus cannot be displaced again. One problem in this context is that it is not practically possible without a tool, i.e. a pointed object, to move the lug as far rearwards as to reach the intended position. By using a catheter having a catheter housing of reduced dimensions, it has been possible to make smaller the opening in one short side of the sheath, through which pass the needle and the catheter supported thereby. Although this may be considered to be an advantage, this solution must be rejected, since the catheter employed cannot be used in medico-technical equipment from other suppliers, which nowadays is a condition for efficient health care. Moreover, one has not been able to cope with the problem of blood, adhering to the needle, dripping from it and through said opening in the short side of the sheath or the slot therein, which obviously exposes the medical personnel using the device to the risk of infection.
Another major drawback is that most of the prior-art solutions are complex, involving a complicated design which entails comparatively high production costs.